Reichardt



May 27, 1958 P. REICHARDT 2,836,255

MEDICAL ACOUSTIC DEVICE Filed Dec. 23, 1955 United States Patent MEDICAL ACOUSTIC DEVICE Pierre Reichardt, Brussels, Belgium, assignor to Societe Beige dOptique et dlnstruments de Precision, Societe Anonyme, Ghent, Belgium Application December 23, 1955, Serial No. 555,142

Claims priority, appiication Belgium December 28, 1954 6 Claims. (Cl. 181-24) This invention has as subject a medical acoustic device suitable for sounding the human or animal body, more especially for diagnosis of ailments of the respiratory organs, of the heart, of the larynx, and so on. The device is distinguished from known apparatuses by the high amplification of the intensity of the sounds to be observed and by the complete absence of any background noise produced by the apparatus. These advantages are obtained by simple acoustic means which contain no electric or electronic means.

According to the invention, the device comprises a case with two diaphragms, the tension of which is adjustable and one of which, plane and disposed at the bottom of the case, together with an element acting by inertia delimits an air chamber, while the other, which is tubular, is connected on the one hand to a passage leading from the air chamber through the inertia element and on the other hand to a tubulure which is fastened on the case and which is connected to the listening tubes of a stethoscope. The case and the inertia element have the form of solids of revolution which have parallel generatrices and which are disposed one inside the other and which enclose between them a second air chamber in which the tubular diaphragm is disposed. The inertia element is held in the case by washers of flexible material so as to be able to execute axial movements produced by the air of the first chamber under the action of the oscillations of the plane diaphragm, which oscillations are produced by the sounds to be observed. The axial movement of the inertia element modify the longitudinal tension of the tubular diaphragm and at the same time create in the second air chamber periodic pressure variations which act transversely on the tubular diaphragm.

At its lower end, the case is provided with a rim on which there are fastened and joined one of the flexible washers holding the inertia element, the plane diaphragm, and an angle piece curved to correspond with the diameter of the rim of the case and which protects the diaphragm and which, when placed on the body to be sounded, stretches the skin and at the same time insulates the diaphragm from sounds coming from outside. The top of the case is provided with a means having a rotary knob for varying the tension of the tubular diaphragm and, through the medium of the inertia element, for also giving the plane diaphragm the appropriate tension for the sounding. The inertia element is a solid or hollow body, the natural frequency of which is outside the frequencies to be amplified by the listening device.

The accompanying drawing shows one form of construction of the invention by way of example and the single figure is a diagrammatic vertical section.

The case 1, in the form of a cone or another solid of revolution, is closed at the bottom by a plane diaphragm 2, the rigidity of which is selected according to the par ticular use for which the device is intended. The case houses an element 3 acting by inertia after the style of a balance weight and which is held in place by washers 4 and 5 which are inserted in circular grooves provided on ice 9 its surface. The element 3, of metal or some other suitable material, may be solid or hollow and must have a natural frequency lying outside the frequencies to be listened to. The outer edge of the washer 4 is fixed to the rim of the case 1. The inertia device and the diaphragm 2 enclose an air chamber 6, which communicates through the passage 7 with the inside of a tubular diaphragm 8. The latter is fixed at its upper end to a tube 9, the threaded part of which passes through the plug 10 and the rotary knob 11 and terminates in a collar 12 on which is fastened the listening tube of a stethoscope (not illustrated in the drawing).

The tubular diaphragm 8 may be stretched to a greater or lesser degree by operating the rotary knob 11, thus simultaneously limiting the movability of the element 3, which is resilently held by the washer 4, and thus also influencing the tension of the plane diaphragm 2. Since the washer 5 is perforated, the tubular diaphragm 8 is situated in the air chamber 13, which is delimited by the case 1 and the element 3. The axial movements of the latter, caused by the oscillations of the plane diaphragm 2, have as a consequence a change of the distance between the walls of the conical parts of the case and of the inertia element 3; the pressure changes resulting therefrom react transversely on the tubular diaphragm 8, on the outside of the latter, while the axial movements of the element 3 act simultaneously on the tubular diaphragm 8 in the longitudinal direction.

The relation between the adjustment of the inertia mass and the adjustment of the plane diaphragm 2 is as follows:

During the examination of a patient by means of the apparatus according to the present invention there are three cooperative closed spaces or chambers separated from each other:

(a) Chamber 6 extending through 7, 8 and 12 into the listening tube of the stethoscope.

(12) Chamber 13 and (c) The chamber which is formed inside the ring 14 between diaphragm 2 and the body under examination.

Operation of the knob 11 in the one or the other direction results:

In the regulation of the tension of the tubular diaphragm 8, resulting in its turn in the regulation of the position of the inertia element 3.

Resulting in its turn in the regulation of the volume of closed chamber 13 and of the gas pressure in this latter.

Resulting in its turn in the regulation of the gas pressure (through tubular diaphragm 8) in closed chamber 6, 7, 12, listening tube.

Resulting in its turn in a regulationof the tension of diaphragm 2, as the latter is subjected to the ditferential pressure equal to the pressure ratio:

It will be seen from the above explanations that operation of knob 11 will cause simultaneous modification of the tension exerted through tubular diaphragm 8 on the inertia mass 3, and of the ratio of pressure within 13 to pressure 6, 7, 8, 12 hearing tubes to pressure within 14 between 2 and the body of the patient, and that said modification causes the adjustment in question.

A cylindrical part 14, constituted by an angle piece curved to the diameter of the plane diaphragm 2, surrounds the latter on the one hand to protect it and on the other hand to insulate it from external sounds. To use the device, the cylindrical part is pressed against the skin for the purpose of stretching it and rendering the apparatus solid with the body to be sounded. Together with the diaphragm 2 and the washer 4, said cylindrical part is fastened on the rim of the case 1 by an appropriate means, for example by crimping. If desired, a palpater may, in accordance with current practice, be fastened to the plane diaphragm 2 to localise the sounds.

The invention is naturally not limited to the form of construction described and illustrated by way of example, and modifications may be made to it without thereby departing from the scope thereof.

I claim:

1. A medical acoustic device comprising in combination a housing, a plane diaphragm closing the bottom of the housing, an element resiliently supported in said housing above said plane diaphragm and forming a first cham-' ber therebetween, a tubular diaphragm fixed to the top of said element to communicate between the said first chamber and the top of the housing, and a second chamber formed between the said element and the top and side walls of said housing. 7

2. The invention as set forth in claim 1, wherein the axis of symmetry of the said tubular diaphragm is normal to the said plane diaphragm.

3. The invention as set forth in claim 2 wherein the said housing and the said element have the form of solids of revolution having mutually parallel generatrices.

4. The invention as set forth in claim 3, including resilient means joining between the said element and the said housing to allow motion of the said element in axial direction.

5. The invention as set forth in claim 4, including adjustable means joined to the said tubular diaphragm to vary the tension thereof and transmit tension to the said plane diaphragm through the said element.

6. The invention as set forth in claim 5 wherein the natural frequency of the said element is distinct from the frequencies of interest in the use of the device.

References Cited in the file of this patent UNITED STATES PATENTS 2,755,880 Hofmann July 24, 1956 

